How can I make multi-domains in s3 for uploading photos?

Question

Ruby on Rails

I use S3 to store photos. The application has a page on which there are a lot of photos. I would like to speed up their loading. I remember once there was a way to do this, you had to distribute photos from several domains, then the browser could upload several photos at the same time. How can this be implemented in s3 and rails?